How to access rows in DataGrid,silverlight 4?

hi,

in my grid i have one checkbox column and one string column. my requirement is to get the selected check box related string value.

ex: if i select 1st and 3rd row checkbox, i have to retrieve 1st and 3rd row string value.

this is my datagrid code.

<sdk:DataGrid SelectionMode="Extended" AutoGenerateColumns="False" Height="282" HorizontalAlignment="Left" Margin="12,90,0,0" Name="DG_attachments" VerticalAlignment="Top">
<sdk:DataGrid.Columns>
<sdk:DataGridTemplateColumn Header="Select">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox x:Name="CheckName" HorizontalAlignment="Center" VerticalAlignment="Center" />
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
<sdk:DataGridTextColumn CanUserReorder="True" CanUserResize="True" CanUserSort="True" Header="Attachment Name" IsReadOnly="False" Width="Auto" Binding="{Binding Path=Name, Mode=TwoWay}"/>
</sdk:DataGrid.Columns>
</sdk:DataGrid>

please help me by giving some sample code to achieve this .!

i would be much thankful for your help.